Grid construction



1943- c. M. WHEELER I ,310,8

GRID CONSTRUGTII'ON Filed Feb. 14, 1942 IN VENTOR. 04/?6 IVM WHEELER ATTORNEY.

Patented Feb. 9, 1943 UNITED STATES PATENT. OFFICE GRID CONSTRUCTION Carson M. Wheeler, Montclair, N. .L, assignor to Federal Telephone and Radio Corporation, a corporation of Delaware Application February 14, 1942, Serial No. 430,909

8 Claims.

' 'This invention relates to vacuum tube electrodes, and particularly to grid-like electrodes.

The object of my invention is to provide a grid-type electrode construction which permits easy assembly and which will not readily warp and deform under changes of temperature. I It has been customary to construct grid or grid-like electrodes by attaching wire helices or equivalent meshes to supports which are mounted in a suitable manner in the tube. It has commonly occurred that heat developed within the tube during operation has been unsymmetrically distributed throughout the grid structure so that the structure would become deformed and moved out of its "proper position within the tube. In accordance with my invention, there is provided an assembly 'of thesupports and grid arranged to minimize the tendency toward the physical distortion.

The invention will be understood from the following detailed description and accompanying drawing, of which Fig. I shows a longitudinal mid-section of a grid-like electrode construction in accordance with this invention:

Fig. 2 is an end view of the structure of Fig. 1;

and

Fig. 3 is an enlarged cross section view taken at line 3--3 of Fig. 1.

The drawing illustrates an electrode which may be used as a control grid or screen electrode in a vacuum tube. The electrode may be normally centrally located within a tube, and may be mounted on a metallic base member ID having a thin cylindrical collar portion ll sealed to are-entrant part of a glass envelope l2, the glass envelope being only partially shown. There is formed from the collar of the base member II], a flat ring portion l3 of sufiicient width to receive supporting rods l4 through holes in the ring l3. The supporting rods l4 also pass through suitable holes in an annular ring member [5 which is spaced from ring l3 by spacing sleeves l6 placed over the rods. The ends of the rods are threaded so that nuts I! and I8 may be turned to tighten the rings l3 and I5 against sleeves IS.

The opposite ends of supporting rods M are passed through an annular ring l9 to which they are fastened, as by welding, at 20, The ring I9 is provided with a plurality of holes other than The number of holes herein is a satisfactory number. The three rods 21 which are passed through the three alternate holes 22, 24 and 26am threaded, and 'the portions'of the ring 19 around the holes through which these three rods pass are rounded out on both surfaces of the ring to form spherical sockets for spherical ended nuts 28 and 29, as shown in Fig. 1, so that the cooperating surfaces of the nuts will fit in the sockets. The holes 22, 24 and 26 are made of sufiiciently larger diameter'than the rods 21 to provide a substantial clearance from the rods passing through them so that the rods may have considerable leeway of movement in the holes, and the nuts may be tightened down to seat with the rods in any desired position within their range of adjustment.

The other three rods 21 are passed through the remaining alternate holes 2|, 23 and 25 which are made to provide a slide fit for the rods. The opposite ends of these latter three rods 21 are passed through a cap 30, to which they are fastened as by Welding at 3|. The rods are dimensioned so that when the three rods fixed to the cap at 3| are slid through holes 2|, 23 and 25, the other three rods which are fastened by nuts 28 and 29 to the ring l9, do not-quite reach the cap 30, but lie within the inside of the collar 34 thereof. In assembling the grid, the grid supporting rods 21 willgenerally be placed in their proper relative positions in a suitable holdingdevice, and the grid element, shown in the form of a'wire helix 32 will then be wrapped around the rods and suitably attached-to the rods at its points of contact therewith. A very satisfactory way of attaching the grid wire 32 to the rods 21 is by a notch and swedge arrangement. According to this method the rods 21 are first suitably notched along their outside surfaces at the points where the grid wire is intended to -be placed.- Then, when the gridwire is wrapped around the rods it is placed in these notches, The fastening may then be accomplished by againnotohing each rod at each side of each grid wire so as to knock a small burr of the rod metal against the grid wire in the notch. Another suitable method of attaching would be to spot weld the grid wires at their points of contact with the rods.

After the rods 21 and helix 32 are thus assembled, the rods may be placed through their respective holes in ring [9, and the nuts 28 and 29 may be applied to the three rods shown in a preliminary manner without tightening them. With the grid in this position the cap 30 may be brought into position and Welded to the ends of the other three rods 21 as shown in Fig. 2. This supporting ring I9 50 that the grid will properly lie in its desired position; and if necessary the grid may be given whatever slight tilt, relative to the supporting ring, may be found necessary; and the proper adjusting is readily accomplished by manipulation of nuts 29 followed by tightening of nuts 28. The ball and socket construction of nuts 28 and 29 and the cooperating ring member i9 permit the desired adjustment to be made without putting any strain on any of the grid rods, as the nuts will seat without producing strain in any desired position of a rod 21 relative to ring l9 within the range of adjustment permitted by the clearance of the hole through which the rods pass. After being thus adjusted the grid structure may be attached to base member It! by the nuts [8.

In the construction used, the grid structure is supported from the ring i9 by the three rods secured to the ring by the nuts; the other three rods 21 which merely slide through the ring, are supported only by the grid wire attached to all the rods 21; and the cap 39 is in turn supported at only the three points of attachment of the last-mentioned three rods 21. This supportin construction has been found to afford the desired freedom from deformation or tilting of the grid structure as a whole, under conditions of non-uniformity of temperature in the different parts. The grid is ordinarily placed within a vacuum tube around a centrally located hot cathode which heats all the part of the grid. Due to local conditions, some of the rods 21 are likely to become somewhat hotter than others and thus expand a little more. The construction used herein permits the rods to expand nonuniformly as individual rods without tilting the grid, because a greater expansion of one rod will not strain the next rod which may not expand quite as much, inasmuch as said next rod is not fixed to the same member i 9 or 30. For example, an excessive expansion of a rod which is fastened to ring l9 by the nuts will not tend to tilt the cap 30 because the rod will simply elongate within the collar 34 of the cap. Likewise an excessive expansion of a rod which is attached to can 30 will simply cause such rod to protrude a little further through its clearance hole in ring l9 without tilting the cap. Thus, while the several rods 21 may elongate and contract relative to each other, there will be no change in the position of the grid structure as a whole relative to its supporting ring [9 or a cathode placed within it, and the only change may be a slight displacement of some side of the grid helix, which is of little importance.

It will be further understood that the rods fastened to ring I9 need not necessarily reach the collar 34, and the rods which are welded to cap 33 need not necessarily reach to the ring I9, as the attachments of the grid helix to the rods is sufiicient to keep the structure in position. Some additional security from damage is doubtless afiorded, however, by extending all the rods from within the collar 34 to a sliding engagement with ring I 9, as shown.

What is claimed is:

1. A vacuum tube grid construction comprising a plurality of grid rods extending between a supporting annulus and a collar member, a grid wire fastened to said rods, some of said rods being fastened to said annulus and movable relative to said collar, and other of said rods being fastened to said collar member and movable relative to said annulus.

2. A vacuum tube grid construction comprising a plurality of grid rods extending between two supports, at least one of said supports being annular in, shape, supporting means for holding 'said annular support, some of said rods being fixed to said annular support and slidably related to the other support, and other of said rods being fastened to said other support and slidably fitted through said annular support.

3. A vacuum tube grid construction comprising a plurality of grid-rods, a threaded endportion on each of said rods, a grid attached to said rods, a supporting member for said grid provided with holes, said holes being rounded out at each end, and adapted to fit loosely over the threaded end portions of said rods, a pair of nuts for each rod having rounded faces, said nuts being screwed on said rods on opposite sides of said supporting member with their rounded faces extending into the rounded out holes in said support, whereby the position of said grid may be adjusted in reference to said support.

4. A vacuum tube grid construction compris ing a plurality of grid rods, a threaded end portion on each of said rods, 2. grid attached to said rods, a supporting member for said grid comprising a fiat ring-shaped member provided with holes adapted to fit loosely over the threaded end portions of said rods, means for adjustably securing said grid to said supporting member comprising a pair of nuts provided with rounded faces screwed on each rod so as to engage with their rounded faces the opposite sides of said member, and a complementary recess formed around each end of said holes to receive the rounded faces of said nuts.

5. A vacuum tube grid construction comprising a plurality of grid rods, a threaded end portion on each of said rods, a grid attached to said rods, a supporting member for said grid comprising a fiat ring-shaped member provided with holes adapted to fit loosely over the threaded end portions of said rods, means for adjustably securing said grid to said supporting member comprising a pair of nuts screwed on each rod so as to engage opposite sides of said member, other grid rods disposed between the first-mentioned grid rods also secured to said grid, said supporting member being provided with holes for slidably supporting an end portion of each of said other grid rods.

6. A vacuum tube construction according to claim 5 in which a cap member is provided for supporting the opposite ends of said other grid rods, said grid rods being secured to said cap member in spaced relation.

7. A vacuum tube construction according to claim 5 comprising a second supporting member secured to the tube envelope, and means for supporting the first mentioned supporting member comprising a plurality of supporting rods se cured thereto, and means for securing said rods to said second supporting member.

8. A vacuum tube construction according to claim 5 comprising a second supporting member secured to the tube envelope provided with a plurality of holes and means for adjustably supporting the first-mentioned supporting member comprising a plurality of rods secured at one end in spaced relation to the first mentioned supporting member, a threaded portion at the opposite ends of said rods adapted to enter the holes in said second supporting member, and nut means on said threaded portion of said rods for adjustably securing said rods to said second supporting member.

CARSON M. WHEELER. 

